It
has been shown that the accuracy of solution for atmospheric
pollution dispersion problems is highly dependent on the computational
mesh and in particular the degree of resolution. Course meshes
have difficulties in resolving a large amount of the structure
resulting from multi-scale source problems and complex meteorological
fields. Finely resolved meshes on the other hand are computationally
expensive and often prohibitive for reactive flow problems with
a large number of chemical species. A solution to this problem
is to provide extra resolution of the mesh where large solution
errors or steep concentration gradients exist, leaving a course
resolution elsewhere. In this way computational resources are
utilised where they provide significant gains in accuracy. This
paper presents a 3-D finite volume reactive flow model based
on a transiently adaptive unstructured mesh. The use of tetrahedral
mesh elements allows fully 3-D adaptivity and the flexibility
to enable the code to handle complex structures arising from
source terms of very different spatial scales. The paper will
address issues such as mesh refinement criteria, the efficiency
and accuracy of solutions resulting from different refinement
methods, and the interpolation of emissions/meteorological data
onto the unstructured mesh. Examples will be described for a
number of different pollution dispersion problems covering a
range of meteorological conditions. Results will demonstrate
that the adaptive model is capable of achieving accuracy close
to that of fixed high resolution meshes at a fraction of the
computational cost.